Pneumatically controlled hydraulic prop



May 12, 1953 J. M. TowLER PNEUMATICALLY coNTRoLLED HYDRAULIC PROP 2 Sheets-Sheet 2 Filed Dec. 2, 1949 Z 7 6 Y p/ m 2/// E m n n M 7 m/\95 M v r V .l UW 72 M v m M N -.1 IH.. -I i V mmlmmwmmmmmmm 3 4 .w/ M 5 a :Bh'n Maurice Towle? By am' Y` gb Attorneys Patented May 12, 1953 UNITED 'rss @Param OFFICE .QPNEUMAITIGALLYII.ooNrRoLLED l1:infnasomo raor "Thisinventiomrelates to pneumatcally convtrollen' hydraulicipropforsupportingheayy. loads x hydraulic "cylindereand-'ram #assembly the comhydraulic assembly inthe..extensioniancontrac- `'liie prop. may. .,.haye ,provision fonperation :roi

the check :valve by` a;.confinementiofA ,thelpneumatic :device Iin` order. .to,pass,lhydraulic "luid' fromaithe ...hydraulic cylinder lto .'Jthe .cinteriorx of Hthe ...-,hy-

lilraulic ram duringncontraction oiltheiprop.

YThe, pronmay. be Jtte'cl-ailitl'aarnauxiliary val-re contrived to .Iopensimadyaneecthe checkvyaiye hydrauliccomponent toA theotherzatfxa; greatiyq-er stricteci.` fratezI- atutheflstarti.ofmIcontractionoofzmhe Iprop.

I.The propsmayphavefaxreliei .'Iyalveffadaptednto open when the pressure in the hydrauliccylder duid front/.saidI cylinder itothe interior tof Ithe zIhydraulic'iram.

. Y Ari-'exampleroffayhydraulicgprop embodying the invention is.;shown,.finf.thenaccompanyng'I-draw- .,ings,I.in whichfEig. 1,;isia yertealwsectiorrishowing .the prop in tsinormally extended state-,rand'igi 2 is a vertical sectionshowing;:theaprpptasiitsstarts .,toicontract.

In [the drawings. theicylinderio .-,theihydraulic ,cylinder-.anderam ,assembly iscdenotedrbw laand the rain.I ist clenoteduhya 2. .Lina,thenexampletithe hydraulic cylinder I is thellowe componentzof .the prop..Yand'ethe,hydrauiica:1:amr.2.isutthezillpper ^component.

. Theram ,2 ais.I alholiow lrlbodymitlu a rroofsengagmacan `3. The` body A,ofstthe r ramfiis .totatlyyem closed .except that /it;1-,has a Il.centralz.,elandsll;f the check-I `valye .tancla-a relief. valve t. in,.its,bottom TI ;.,and `,there sis.. an .opening 3 :.in. afitsttopfl .9, 4into which ...ang indicator ...imthei formgof-a whistle III ,isi fitted. This `Whistlemis smmaderthatytaaimis .,blowntintolitlthroughithei openng ,thei whistle Wili sound. 'lin use'ofithe: prop, the space "S en- (Ciani-sa) y1I-I2 ciosed by the` cylinder I and rain-2f Iis lcompletely illed'I and' the ram=I2 -isl partly filled with hydraulic fluid; namely -oi1^ 3 I The pneumatic controledeyice includes a `rig- 5 -fidly f stationary 'Iramccmprising `la composite frod that 'consists of 'inner and outer eze-axial 'tubes Il fandflEI-:securedfto' the hydraulic cylinderf'oase NFA@ and a'piston I3Iat1the top'of both tubes. 'The outer `tube `I 2 has' a sealingI sliding itthroughthe fgl-anclfId .IinIthehyiirenilicrarnr I:bottom l. I The I `pneumatic Icontrclidevicealsoinciudes a I cylinder z-III lI,III which contains I'the 1I piston I and=-is `located Iinside the hyolraulic yrarrrI4 2. "'f'lhe Alower-endI of the pnenrnatic cylinder I-II is formed I* asa neck V 2J-MA slidable' on the outer tube 'I I@ ibut isother- 7Hwise `closed,"whereasftheupperenci or the cylin- 'IderI III ineens"throughA ports I'I i 1into the inside of .the hydraulic ram'' "I- The" pneumaticI` cylinder Il l yis-moyable'notl only withfthehydraulic Irani 2 but toyasmall extent Irelativelyto it. `I `Theinner and outer tnbes I II I and' I2 constitute I separate-I air conduits Iir and1 I 2. The central conduit 'i tv opens -through therlpneurnatic- -pston I. I 3 I to theV open rupper end of the-pneumatic cylinderI Iipand the Nvmatic pistonA I 3 intothe' closed LIlower endi of the pneumaticycylinder"IIi. Normally, the pneumatic WJcylinder Itcomes against the hydraulic-ram top,

andthef'whistle I I il is kept; closed by a part I 2 I on the pneumaticecylinder ytop.

i .The check-varient is* anonreturnfvalve, which 'normallyiis `-kept" tightly closed" against Y,its :seat

"I 9 byfa` y:spring 2l). TheV valve; 511sy associatedwith `1ati22"onthebottom "i orthe hydrauiicwrarn and 'llTherreliei Valve 6 also is non-return and spring# pressed, `the yalvehaving aisprine'glti kadageted to 0 open iitfgfromV its seat: ISA Vwhen'the ,pressure in "the hydraulic cylinder. I,.exceeds ajlirnit; inthe Aexample this limit' .is J one .tonper squaren inch, I corresponding tofa. load on the, prop, ,of I. about one .hunclredand fifty tons.

The ,check .I yaiye.- 5 isintted `with .a.,.no.rmaily Lclosed, springgpressed, auxiliary .non-return yalve 2L Which canbe opened by,thpnenmaticcyh .inder' HI. Thisauiiliary.yalye'zilficontrols alsmall opening 2 5 1 leadingv through.. thecheck valve.. by 50 way ,ofports .26 wand. an.;annular.passage Tito ...theinsideoithe ram 2.

The pneumatic device II-to Il! is suppliedirom can external source of .a compressed... air ...through anmappropriate controlyalye (not. shown) ,in

"65. communcationwith the two. air conduits It and l 'i by way of ducts 28 and Ez respectively extending through the base IA of the cylinder I to the exterior of the prop.

In use of the prop, it must rst be extended t engage tightly between the door A and roof B o a mine. To do this, a worker manipulates th control valve so that compressed air passes through the central conduit i6 and the upper end of the pneumatic cylinder le into the hydraulic ram s and, pressing upon the hydraulic iiuid 3l therein, forces the check valve ii to open against the yielding resistance of its spring it and forces oil from the ram into the space S within the hydraulic cylinder l Thus, the ram 2 is forced to rise and its cap 3 engages the roof, exercising an initial holding pressure which may be of the order of thirteen tons. As soon as the ram 2 comes to rest against the roof, the oil flow through the check valve 5 ceases, so. that the check valve closes under the influence of its spring and locks inside the hydraulic cylinder l the oil filling it. The pressure inside the hydraulic cylinder may now increase to any extent (say, under subsidence of the mine roof B) as far as the limit for which the relief valve is set, without any contraction whatsoever of the prop.

When the prop is Vbeing extended in the manner described, if the operation should be continued beyond the full-extension limit (for instance, there might be a looseness or opening in the roof) a warning is given by the whistle il?. At the limit mentioned, the pneumatic cylinder id (rising with the hydraulic ram 2) is stopped by meeting the always stationary pneumatic piston i3, so that the Astill rising hydraulic-ram top f '9 leaves the pneumatic-cylinder top part lll and uncovers the whistle Ill, which is then blown by compressed air from the pneumatic cylinder.

In the event that the prop is to be contracted, say for removal, a worker manipulates the control valve so that compressed air passes through the outer conduit l1 inte the pneumatic cylinder below the piston i3'. Such air forces down the pneumatic cylinder, which initially strikes and opens the auxiliary non-return valve 24, so that the oil escapes from the spiace S within the hydraulic cylinder l at a very low rate. Thus, the prop starts to ycontract very slowly under its roof load. After a very short descent of the pneumatic cylinder I4, as Fig. 2 shows, this cylinder makes contact with the lever 2l, waich as the descent continues opens the check valve 5. so that oil may now pass at a higher rate from the hydraulic cylinder l, and the speed of contraction of the prop correspondingly increases. When the roof load ceases to depress the hydraulic ram 2, the pneumatic cylinder lli in its continued descent (relatively to the now stationary hydraulic ram) engages the hydraulicram bottom 'l and forces the ram to descend until either the compressed air is cut olf by the worker or the ram is fully contracted.

It will be manifest that, in regard to oil supply, the improved prop is a self-contained unit.v

One 'advantage of this is that each time the prop iii sured that when the Cil is dismantled for testing and overhaul (say once` or lperhaps twiceper year) it can be given a supply of truly clean oil, and this is an essential to drop tightness that is to say, complete sealing against escape of -oil from inside the hydraulic cylinder so that the prop does not contract to any measurable extent throughout each period of use.

Another yadvantage of the improved prop is that, once it is set in position, it is independent i prising a hydraulic cylinder-and-ram of external power and therefore of diiliculties due to failure of power supply, burst pipes, leaky connections and valves, and broken fittings.

Another advantage is that the hydraulic valves and working parts Iand the hydraulic connections are all housed in the interior of the prop, where they are safe from damage and dirt.

Seeing that the operation of the prop is effected by pneumatic power, there is also the advantage that provision of costly highpressure hydraulic plant is avoided, notwithstanding that the improved prop is itself a high-pressure hydraulic appliance. Moreover, quite a simple pneumatic power plant will suffice 4ifor a large installation of props.

By virtue of the auxiliary valve 24, it is enprop is being contracted there is an initial period, which need only be of brief duration, during which the pressure on the roof B is reduced gradually. Once that period has passed, the prop is rapidly contracted. The arrangement is such that this sequence of operations occurs automatically, being out of the control of the operator.

I claim:

l. An extensible and contractible prop comassembly the main components of which are a cylinder and a hollow ram in telescopic relation, a space enclosed by the cylinder and ram components being filled with a hydraulic iuid, a normally closed check valve in the ram component, said valve being adapted to open in the direction t0- wards said hydraulic-fluid-lled space and when opened forming a passage for the hydraulic iiuid from one of said components to the other, a pneumatic control device mounted inside one of said components and co-operating with said check valve, means for conducting pneumatic fluid into said device to actuate it so that it forces the check valve to open and release hydraulic duid from the hydraulic-iiuid-fllled space, the control device in this event engaging the component containing it and thus forcing the prop to contract, and an outlet for the pneumatic fluid from said device into the interior of one of said components to apply pneumatic pressure to hydraulic iiuid in this one of the components in order to cause this Huid to force said valve to open so that the hydraulic fluid flowing through the valve into said space will force the prop to extend. f

2. An extensible and contractible prop according to claim l including also an auxiliary nonreturn valve carried by the ram and arranged to co-operate with said pneumatic control device, being engageable `by said device to open in advance oi' the check valve and pass the hydraulic duid from-one of said components to the other at a restricted rate.

3. A'n extensible and contractible prop according to vclaim 2 in which said check valve has a through passage and said auxiliary non-return valve is mounted in said check valve and controls said passage. f

4; An extensible and contractible lprop according to claim 1 including also a lever fulcrummed on the hollow ram and interposed between the pneumatic control device and the check valve,

open in advance of the check Valve and pass the 8 hydraulic uid from oneof said interiors to the other at a restricted rate.

JOHN MAURICE TOWLER. References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 250,103 Reynolds Nov. 29, 1881 1,299,668 Blomqust Apr. 8, 1919 1,797,297 Ringle Mar. 24, 1931 1,899,534 Steedman Feb. 28, 1933 2,085,961 Dorward July 6, 1937 2,336,808 Simon Dec. 14, 1943 

